All-Sun EM285 is the best electrical tester for reducing diagnostic time in automotive electrical systems.
Connect this item with an automotive battery. And then the end of its probe will detect the positive or negative voltage through switch.
EM276 Injector Tester can diagnose injector problems, you can use it on each injector individually to test stuck, leaking or burnt-out,which used 12V vehicle battery as power supply,it has 4 pulse modes and in the continuous working mode (mode 4) and can help you identify the injector good or not when you switch off the engine.